The green-eyed frog is classified as Vulnerable (VU) on the IUCN Red List (1).

Named for its distinctive green eyes, the green-eyed frog (Lithobates vibicarius) is a relatively large frog species with quite variable colouration. Adult green-eyed frogs range from bright green to brassy or reddish-brown on the upperparts, with varying amounts of darker spotting. There is a dark or yellowish-brown stripe running along the side of the face and body (2) (3) (4), bordered above by a narrow, greenish-gold line. There is also a light stripe along the upper lip (2) (3). The limbs are green or yellowish-brown above, with some brown and gold speckling (3), while the rear surface of the thigh, and often also the underside of the thigh, are bright red (2) (3) (4).

The green-eyed frog has a fairly short, wide snout, which looks pointed from above. There is webbing between the toes of the hind feet, and the toe tips are expanded (2) (3). Female green-eyed frogs are generally larger than the males (2) (3) (4). The tadpoles of the green-eyed frog are large, at up to seven centimetres in length (2), and are generally brown, with a paler underside and a paler tail fin, which has dark spotting (2) (3) (4).

The call of the male green-eyed frog is notable for its softness, which is thought to be related to a lack of vocal sacs. Males produce two types of call, described as a harsh trill and an untrilled note (2) (3) (4). The trills are given up to five times in succession and may be followed by up to three untrilled notes (3).

Once widespread across the Cordillera de Tilarán, Cordillera Central and Cordillera de Talamanca of Costa Rica and western Panama (1) (2) (3) (4) (5), the green-eyed frog is now restricted to Monteverde and the Parque Nacional Juan Castro Blanco in Costa Rica (1) (6).

The green-eyed frog inhabits humid montane forest and rainforest, at elevations of around 1,500 to 2,700 metres (1) (2) (3) (5). Although it prefers dense forest, it has also been found near water bodies in clearings or pastures (1) (2).

This species is semi-aquatic, and breeds in shallow ponds, slow-moving streams or in puddles (1) (2) (3) (4).

Male green-eyed frogs usually call at night, from vegetation in water (1) (2), and sometimes join together in choruses of up to a hundred or more individuals (2) (4). Due to this species’ quiet calls, these choruses may only be audible at relatively short distances (2) (4).

The breeding season of the green-eyed frog may coincide with the early rainy season, between May and July (2), although eggs have also been found between November and May (3) (7), and some studies report breeding to occur year-round (2) (4). The eggs are laid in globular masses, which measure around ten centimetres across and are attached to vegetation or rocks (1) (2) (4). Green-eyed frog tadpoles appear to have a long development period (3) (7).

Little other information is available on the biology of the green-eyed frog, but adults are reported to be active by both day and night (2).

Once common in Costa Rica, the green-eyed frog has undergone a drastic decline and was feared to have gone extinct in the country in the 1990s. Fortunately, a population was subsequently rediscovered near Monteverde (1) (6), and in 2007 a second population was discovered near to the Parque Nacional Juan Castro Blanco (1). Unfortunately, the green-eyed frog appears to have disappeared from Panama (1).

The main cause of the decline in the green-eyed frog is believed to be the fungal disease chytridiomycosis (1) (8). There is some evidence to suggest that under natural, unstressed conditions the green-eyed frog can remain largely unaffected by this disease (6), but its effects could be compounded by a combination of other threats, including pollution, climate change and habitat loss (1) (7). Agricultural chemicals have been blamed for a high level of deformities and a lack of tadpoles in the recently discovered population near the Parque Nacional Juan Castro Blanco (1).

Conservation work for the green-eyed frog has included assessing and monitoring the wild population, raising local and global awareness of amphibian conservation in Costa Rica, and establishing a captive population at Chester Zoo, in the UK (6).

It will be important to continue monitoring the status and health of the remaining green-eyed frog populations, and to protect and maintain the species’ habitat at the two known sites at which it occurs (1) (6). This rare amphibian would also benefit from further research into its biology, behaviour and genetic diversity, as well as from fieldwork to determine whether it still occurs at any other locations (6).